This application relates to techniques, apparatus and systems for vehicle muon tomography imaging.
Muon tomography is an imaging technique that produces an image of an object such as a vehicle or its contents based on detection of the scattering of cosmic ray produced muons as they pass through the object. Muons scattered by an object can be detected and the detected signals can be processed to provide specific density and three-dimensional imaging of materials.
The collision of natural cosmic rays with atoms in the earth's upper atmosphere creates unstable particles, such as pions and kaons, which decay to muons. Muons penetrate through the atmosphere and into the ground at the rate of approximately 1 per square centimeter per minute. Muons can be thought of as much larger cousins of the electrons that are an essential part of ordinary matter. Energetic muons interact strongly enough with matter by ionization to be easily detected, and can penetrate large thicknesses without significant impairment.
Physicists at the Los Alamos National Laboratory (LANL) have developed techniques for detecting scattering of cosmic ray produced muons to produce tomographic images of an object exposed to the cosmic ray muons. See, e.g., Priedhorsky et al., “Detection of high-Z objects using multiple scattering of cosmic ray muons”, Proceedings of SPIE Press, Vol. 5199A-39 (August, 2003). As a muon moves through material, Coulomb scattering of the charges of subatomic particles perturb its trajectory. The total deflection depends on several material properties, but the dominant parameters are the atomic number, Z, of the nuclei and the material density. The LANL techniques are based on precise reconstruction of individual muon tracks and are capable of detecting and visually representing potential threat objects in vehicles or transportable containers in order to alert responsible authorities, thereby allowing them to preemptively interdict the movement of such material to prevent any damage and destruction. A vehicle muon tomography system can be constructed based on the LANL techniques to provide hazard detection at various locations including ports and checkpoints. For example, such systems can provide the Department of Homeland Security (DHS) with an effective solution to the critical need for timely vehicle and cargo inspection nationwide.
Various aspects of muon tomography imaging techniques are described in literature. See, e.g., Jenneson, “Large vessel imaging using cosmic-ray muons”, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 525, Issues 1-2, Pages 346-351, Proceedings of the International Conference on Imaging Techniques in Subatomic Physics, Astrophysics, Medicine, Biology and Industry (June, 2004); and “Muon imager searches for smuggled nuclear material”, OE magazine, SPIE (September, 2003).